Content note: This post contains a lot of descriptions of sex, including fetishes and kinks.
I went on testosterone under the premise that my libido was already so high that it wouldn't be a big deal. Another trans man, when I excitedly asked about the first couple months, said that I would feel like a terrible person for a while, but that I wasn't. I didn't believe him. "I'm already used to wanting sex all the time, and am into all sorts of weird shit, so I'm sure it'll be fine" was my thought process. If I could handle an awkward vore fetish on the onset of puberty, I could handle anything!
And, well... I was wrong. I was super wrong. I was embarrassingly wrong.
It wasn't just an increase in libido. It was a shift in the entire scope of what I was looking for from sex. Where my main drive before T was connection with people, after T it was an insatiable need for orgasm. I could not sleep without having an orgasm. Sometimes in the middle of the day I wouldn't be able to concentrate without coming. And the triggers for this started getting... bizarre. And that's an understatement. Although I needed daily orgasms, I could not actually achieve said orgasm at all without vividly imagining very intensely disgusting things, things I never wanted to actively participate in but which were nonetheless unsettling at best and sickening at worst.
Keep in mind that I already had thought I was disgusting for years, due to the aforementioned fucked up fetishes I acquired as early as puberty. I had only just gotten over that shame, only to put myself in a situation where it was much, much worse.
Talking to other trans men as well as cis men and trans women who had all at some point gone through a testosterone bath, this was totally normal. My roommate once blurted out one of the bizarre, disgusting things that popped into his head while horny--I'm not going to put it here because it's really, really, really bad--and what struck me was how incredibly similar this was to the horror show inside my own head.
This is something really hard for cis women to understand a lot of the time. Cis feminists, for instance, regularly bring up the idea that certain things that turn adult men on are problematic and therefore not natural. This makes it really stressful when you go through that testosterone bath only to find that your sexual tastes became traumatically fucked up even though you know that the things you picture when you're horny are not right. You start thinking, in your shame, "do I secretly want to do this shit?"
The answer for most of us will be an emphatic "no." For me, I found out that I was aroused by some things explicitly because I never wanted to do them, something I have a hard time explaining to myself let alone the goddamn internet. One time I read a great letter in Playboy. Somebody had written in explaining how he, although he was straight, had fantasies involving being fucked by other men. There was the suggestion that maybe he was bi, but somebody else wrote in to say that he had the exact same thing happen. I think people are really quick to rush forward and proclaim that these are really latent queer people, but having gone through this, I seriously doubt it. Testosterone compelling people to explicitly get turned on by things they absolutely do not want is a thing that happens.
I don't want you to think that going on T will make you some sort of threatening fuck monster, because it doesn't really work that way, and yes, you can control your actions just fine. But it snowballed into something really uncomfortable and unsettling, one problem creating another and another. It started with the high libido, which would give me a reckless urge to orgasm. So I'd want sex really bad, but there was a problem: I didn't really want sex, I wanted to orgasm. So all my sexual activity was really targeted on getting to that point. I couldn't handle slow, sensual sex very well because it would frustrate me, in addition to the vaginal thinning that made me bleed whenever I tried penetration. In fact, the sheer number of times I'd make myself come meant I was chronically raw and could barely feel anything anymore, so stuff I would have enjoyed before T became irritating at best and painful at worst. This snowball falls onto partners, who think they're doing something wrong when really your body is just a complex sexual Rubik's cube that nobody understands (including yourself).
After I went off T, my libido tanked. Hard.
In fact, it's lower than it's ever been in any time in my life I can remember. Now, for instance, I rarely ever masturbate before bed, something I already mentioned I'd needed just to get to sleep not very long ago. I think about it, realize "nah," and sleep instead.
It was, by the way, very difficult to explain to my partner after I went off T why this extreme tanking of my sex drive is actually a good thing. But wanting to orgasm without actually wanting sex is not conducive to a good relationship with somebody who wants lengthy, enjoyable sex, especially when it's hard to achieve that climax without having intensely terrible mental pictures that have nothing to do with your partner.
Since my sex drive tanked, I haven't really felt driven to orgasm. There is no singular, overwhelming drive to come, which overall makes sex better rather than worse. I like it, but I don't crave it. Because of this, I also don't burn myself out so much. My sensitivity issues are gone (owing both to not overdoing it anymore and to physical changes causing better lubrication and less thinning), meaning it's no longer painful. This means when I am with a partner, there's no rush to the finish line anymore. There's no pain or bleeding or other shit like that, either (usually). It's so much better, like ridiculously better.